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Which cap is the best?

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LAN_403

Tesla Fan

Sun Oct 24 2010, 10:11AM

Registered Member #3353 Joined: Sat Oct 23 2010, 11:21PM
Location: Greece
Posts: 90

Hi to all,

I 'm a new member, my name is John and i have a dilemma:
I have a few choices of caps for a SGTC (just in my mind so far) and i would like to know which would you say is the best choice.

1: ICW AP 1uF/1000VDC
-ebay link

-datasheet

2: Panasonic ECW-H 100nF/1250VDC
-Digikey link

-datasheet

3: Unknown Russian made paper-in-oil MBGP-2 1uF/630V
-ebay link

I know that the Panasonic cap is used by Dr. Spark ( ) in MMCs (

used the 56nF/1600V caps but same series) but most people think the Cornell-Dubilier 942C is the best, so maybe the ICW AP is a better choice? It is a polypropylene cap, but i dow not know if it is film/foil or full metal film. According to the datasheet they are ment for high voltage pulse applications.
The PIO are not the best choise, i know, but they are soooo cheap

I 've heard people used the also Russian-made K75 but they later switched to a polypropylene MMC. Do you think it is just a waste of time and money?

If anyone has any experience with this kind of caps in a TC (or RF frequency general) please let me know.

Sorry for the long post, please free to correct me if i made a mistake, any kind of feedback will be appreciated!
John

radioman

Sun Oct 24 2010, 02:30PM

Registered Member #3026 Joined: Fri Jul 23 2010, 02:46PM
Location: Los Angeles, California, U.S.A.
Posts: 54

Tesla Fan,

The unanimous winner in the cap race for tesla coils is the Cornell Dublier 942C20P15K. I got them from Eastern Voltage Research at a reasonable price. I have not been able to blow one out yet! (but I am trying) Donâ€™t waste time on anything else! (I have cats, too!)

Radioman

Tesla Fan

Sun Oct 24 2010, 04:11PM

Registered Member #3353 Joined: Sat Oct 23 2010, 11:21PM
Location: Greece
Posts: 90

Thanks radioman,

Although i knew Eastern Voltage Research (seen there DRSSTC kits years ago), it did not occur to me to look there for caps. There prices are not too bad for both the caps there selling.

But the ICW ones are 1/4 of the price, that is a big price difference. I admit that i do not like to be the first "test dummy" to try them, but maybe someone has tried them out and i get an opinion about them. Let me tell you though, if i can get the right price, i just might be that test dummy (50euros are not THAT much of a sum).

PS I looove cats, had at our house since i was 5 years old, now we got 6

Tesla Fan

Sun Oct 24 2010, 04:25PM

Registered Member #3353 Joined: Sat Oct 23 2010, 11:21PM
Location: Greece
Posts: 90

Cats :

Herr Zapp

Sun Oct 24 2010, 05:08PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

Tesla Fan -

The ICW caps are totally unsuitable for TC use. For example, your 1uF/1kV model has a maximum dV/dt (pulse) rating of only 70 v/uS, whereas the well-proven C-D 942C .15uF/2kV cap has a dV/dt rating of 2900 v/us. I am certain that the ICW caps are simple metallized-film construction, rather than the much more robust film-foil construction. The lack of any current ratings in the datasheet is further reason for concern. The ICW caps may individually be 1/4 the cost of the C-D 942C caps, but if you need to use six of them in parallel to obtain the current-handling capability of one C-D cap, you see the "false economy" of using them.

Dr. Spark may have used the Panasonic ECW-H caps years ago in some of his very early coils, but I believe he now caps uses the C-D 942C caps exclusively in his MMCs.

Save yourself time, frustration and money by going with the C-D 952C caps from the start. Use one of the MMC calculators to help select the MMC configuration that's matched to your needs.

See the "MMC Cap Chart" and/or "JAVAMMC" at:

You can purchase them from a number of sources, including direct from C-D distributors. Go to the C-D website (

), click on the "Services" tab at the top of the page, and select "stock check" from the drop-down list. The most commonly used cap is the 942c20p15k-f. Call the distributor to determine pricing at the specific quantity that you need to purchase.

(In this forum, it's preferred to keep post content "on topic". The kitty photos have no relationship to Tesla coils, so it would be better to route this type communication to a specific individual via a Private Message rather than a forum post.)

Herr Zapp

Tesla Fan

Sun Oct 24 2010, 05:38PM

Registered Member #3353 Joined: Sat Oct 23 2010, 11:21PM
Location: Greece
Posts: 90

Herr Zapp,

Hi, thanks for your info. Seems that everyone seems that the way to is the 942C so i will discard my other options.
I should compared the dV/dt rating, my bad. I am not an expert electronic and i was looking for an "Imax" or "Ipulse" rating on the datasheets. Now i know what dV/dt means (still google-ing it now), thanks!

The Classic Tesla link are looking very very helpfull (i was using this

link to calculate caps in series) , LOTS of "calculators" in there!

I think that i will try to find a 942C distributor in europe if i start building the coil (Eastern Voltage Research has a fare price and shipping to Greece, but as most nice tesla items i found, it is located in the US, so Greek Customs are involved - a BIG no-no)

Thanks for your help!

monokel

Sun Oct 24 2010, 05:48PM

Registered Member #2981 Joined: Thu Jul 08 2010, 01:47PM
Location: Germany
Posts: 35

Herr Zapp wrote ...

whereas the well-proven C-D 942C .15uF/2kV cap has a dV/dt rating of 2900 v/us.

German Coilers like these caps (1250 V DC, 220 nF, dV / dt = 11000 V/Âµs !!!):

Maybe such a high dV/dt is not really needed for all TCs.
If you have several distinct caps beeing suitable for a coil, you can compare prices using the ratio "price per storable energy" (because the price of an MMC is proportional to the total storable energy).
If you consider the best distributor in Germany you may get the WIMA 1250 V , 220 nF caps for 1.40 Euro each

(add 19% tax). Thus you have a ratio of about 8 Euros (about 10.5 US $) per storable Joule (at the allowed DC voltage). But you only get a price of 1.40 Euros per cap if you take at least 100 caps; and if you are a private person, BÃ¼rklin may not deliver.

The 942C20P15K caps (2000 V, 150 nF) cost 3.56 $ at RS electronics

Thus 11.9 $ / Joule.

Tesla Fan

Sun Oct 24 2010, 06:36PM

Registered Member #3353 Joined: Sat Oct 23 2010, 11:21PM
Location: Greece
Posts: 90

monokel,

Thanks, i have seen these caps too, but i remember that there price was high (i think $3,5 was the lowest i found for a small number of caps) and so i replaced them with the Panasonic ECW-H (at $2.59euro each) as an option. About BÃ¼rklin, there discount steps are at 1 - 10 -50 - 100 , so i will go as far as 50 caps, price is not bad at all! I will send a mail to BÃ¼rklin and ask them if they would sell me some caps to know my options.

For me shipping is a major issue, not just because of the high cost when seller is far (usually US), but mostly because of the Customs. I have tons and tons of horrible tales to tell you, i would prefer paying 150euros to get something from europe than 100euros from US, trust me it is better. Unfortunately most tesla stuff i find on the internet, like NSTs, toroids, secondaries, stand-off insulators, big pulse caps ect are located if the US...

I am not sure what is the case with big suppliers (Digi-Key, RS), i think the have local distributors and no customs are involved.

Pinky's Brain

Sun Oct 24 2010, 06:48PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

Herr Zapp wrote ...
I am certain that the ICW caps are simple metallized-film construction, rather than the much more robust film-foil construction.

You would hope Panasonic can be slightly trusted on their datasheets ... and they quote 6000 Volt/us with metallized film (they can grow a film with electroplating to arbitrary thickness).

BTW, I have no idea if they are reliable ... but SR Passives sells polypropylene metallized film capacitors very cheaply (with a rather useless datasheet which doesn't mention dV/dt). Mostly eastern Europe distributors, but tme.eu has them as well. 18.5 eurocents a piece for 100+ 150 nF 1000V DC. Someone on the IRC channel ordered them to try in an induction smelter, no idea how that ended up.

Tesla Fan

Sun Oct 24 2010, 07:08PM

Registered Member #3353 Joined: Sat Oct 23 2010, 11:21PM
Location: Greece
Posts: 90

Before i start this thread i was thinking to give a try with the Russian 1uF/630V PIO, using 56caps (2 parallel strings of 28 x series) to make a 71nF/18KV for only 31 euros (beat that nF/euro!).
Now that i think about it again, if the ICW cap (which is a polypropylene cap) is no good, then the PIO will just be junk, a waste af money and time. And if the price difference between the 942C and the Panasonic ECW is small (20euros for a total of ~100-150euros), i will probably go with the 942C.

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